This invention concerns an electronic time-keeping system of the type which includes a high frequency, high stability oscillator serving as a frequency standard or time base. An electronic frequency divider chain divides the high frequency output from the oscillator and develops one or more pulse trains having a repetition frequency and pulse width suitable for driving an electromechanical time display The display includes an electromechanical motor which drives minute and hour hands through a mechanical transmission. Electronic watches manufactured today of the type described above typically have a quartz crystal oscillator and are commonly termed "quartz mechanical" watches. The term "quartz mechanical" will be used herein in a general sense to mean any electronic watch having a stable oscillator controlling an electromechanical time display.
In particular, this invention is directed to a quartz-mechanical time-keeping system which provides a purely electrical integral hour reset feature.
Quartz-mechanical time-keeping systems typically use purely mechanical hour resetting means -- that is to say, a crown, stem, clutch, gear, intermediate gear, etc. The purely mechanical hour reset systems have a number of significant drawbacks. Some are incapable of being set forward and back in integral hours; few are capable of being reset in integral hours with no loss in the time-keeping accuracy of the watch. The purely mechanical reset systems tend to be complex and are apt to be unreliable. Further, they are apt to be cumbersome to operate.
The prior art discloses reset systems in which certain of the necessary resetting functions are achieved electronically. For example, U.S. Pat. No. 3,901,022 discloses a quartz-mechanical watch in which a single mechanical operator is depressed to close a switch and effect a fast-pulse advance of the minute hand. By watching the minute hand advance, the desired number of minutes can be reset by the operator. Hour reset is quite conventional, however. To change the hour setting of the watch, the stem is withdrawn, causing a sliding pinion to engage a setting wheel which can be rotated in the classic manner to effect the desired reset of the hour hand. The U.S. Pat. No. 3,901,022 suggests that the hour reset mechanism can be of a type shown in the art, for example in Swiss Pat. No. 526,804, which is capable of providing integral hour reset. Thus the U.S. Pat. No. 3,901,022 system, while attempting an electronic reset of minutes, relies on the prior art mechanical arrangement for accomplishing hour resetting.
The prior art dicloses other approaches in quartz-mechanical time-keeping systems for resetting hours and minutes by purely electronic means, for example by developing pulses at discrete frequencies or a spectrum of frequencies which can be injected into the motor drive circuit to effect an advance or retard of the display at a rate chosen by the operator. These prior art patents are not known to disclose integral hour advance or retard by purely electronic means. This limits their utility. A collection of prior art showing electronic watches of the type having electromechanical displays and some sort of electronic reset is listed in the table below. The below list also includes miscellaneous prior art patents directed to various electronic watch reset concepts.
______________________________________ Other Prior Art ______________________________________ 3,707,071-Walton 3,810,356-Fujita 3,756,013-Bergey et al British 1,344,393 3,643,418-Polln et al 3,786,625-Sauthier 3,792,577-Fujita 3,812,669-Wiget British 1,344,648 3,948,036-Morokawa 3,724,201-Bergey 3,810,354-Nikaido et al ______________________________________